Roll-up closure systems utilizing a flexible cover or curtain to cover a portal or opening such as a door or window are known. For example, in U.S. Pat. No. 5,566,736, Crider et al. teach a sealable curtain wherein each lateral margin of the curtain has a strip of hook and loop fastener material affixed thereto, and a complementary strip is affixed to the lateral margins of the structure defining the portal. A first end of the curtain is rigidly affixed across an upper margin of the portal. The opposite end of the curtain can be upturned and connected to a driven take-up roller mounted next to the upper margin of the portal. In this embodiment, an elongated transverse rod is supported within the upturned end of the curtain to maintain tension on the curtain. In a second embodiment, a second elongated transverse rod can be utilized to assist in maintaining tension on the curtain (see FIGS. 1-2 of the U.S. Pat. No. 5,566,736). In a third embodiment, a second curtain can be employed (see FIG. 5 of the U.S. Pat. No. 5,566,736). In any of the embodiments, activation of the driven take-up roller lengthens or shortens the effective length of the curtain(s) while positioning the mating hook and loop fasteners to seal and unseal the curtain(s) to the lateral margins of the portal.
Galvanized steel pipes have historically been used as the transverse tension rods in the roll-up curtain systems described above. Occasionally, machinery (e.g. a forklift) will impact and bend the steel pipe(s). When this occurs, the curtain will not roll-up properly and, as a result, the curtain system and the portal associated therewith must be placed out of service until the steel pipe(s) can be repaired or replaced. Accordingly, what is needed is a tension rod for use in a roll-up curtain closure system that provides adequate curtain tension and structural support, yet is flexible and resilient to avoid damage as a result of impact by machinery and the like.